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PubMed1977

Does the brain actively maintain itself?

All living systems have special mechanisms for combatting entropy; however, the brain has dimensions of organized complexity beyong those manifest in the anatomical structure and physiology of the rest of the body. Reasons are given in support of the notion that the brain therefore must have a special, intrinsic "homeostatic" system for its information bearing structures, and, further, that slow electroencephalographic activity has properties which might make it useful for such an order-maintaining function. Recovery from brain damage is hypothesized to be a byproduct of this process, which may involve a cruder sort of information processing than occurs with such functions as perception and learning. Synchronized EEG activity may be adequate to handle this sort of information processing. Speculations are offered about possible mechanics, on the neuronal level, of slow wave participation in plasticity; for example, one such suggestion is based on findings that electrical fields can influence cellular orientation. The methodology of discovering the distribution within the brain of the hypothetical maintenance system is discussed briefly.

Animals↗
PubMed1976

Oldest horse brains: more advanced than previously realized.

Previous interpretations of early horse brains were based on an incorrectly identified fossil endocast, now believed to be from a condylarth. Newly prepared endocasts of Hyracotherium, the oldest horse and one of the earliest perissodactyls, reveal a relatively larger brain, with a more expanded neocortex, than existed in the condylarth ancestors of perissodactyls. Fifty million years ago, horse brains had suprasylvian, ectolateral, and lateral sulci, but the frontal lobe was undeveloped.

Animals↗
PubMed1979

The brain of two mammal-like reptiles (Cynodontia - Therapsida).

The endocasts of the cynodonts Massetognathus sp. and cf. Probelesodon are studied from descriptive and quantitative viewpoints. The morphology of the casts is described briefly, doing special attention to those features that import to the quantitative analysis, as for instance the general appearance of the casts and some vascular impressions. The general conclusions of this study are: 1.--Massetognathus sp. has had a brain with rather long olfactory peduncles and perhaps not greatly developed olfactory bulbs which could imply a non-macroosmatic condition, up to date not known for cynodonts. Cf. Probelesodon, on the other hand, shows a brain type similar to those of other cynodonts. 2.--Certain cynodonts at least, have had brains that filled fairly well the endocranial cavity. 3.--The cynodonts Massentognathus sp. and cf. Probelesodon, as surely other species, have acquired in Middle Triassic times a relative brain size rather closed to that of certain fossil and living mammals.

Animals↗
PubMed1987

Correlation of morphologic brain lesions with physiologic alterations and blood-brain barrier impairment in 3-nitropropionic acid toxicity in rats.

3-Nitropropionic acid (NPA), a toxin which irreversibly inhibits the Krebs cycle enzyme succinate dehydrogenase, causes severe neurologic disease and a specific pattern of morphologic brain damage when given subcutaneously to rats. To determine whether hypotension or hypoxemia were necessary for development of morphologic brain lesions in NPA neurotoxicity, systemic blood pressure and arterial blood gases were measured in NPA-intoxicated rats. The extent and distribution of albumin extravasation was examined by immunohistochemistry, and was compared to the extent and severity of morphological injury in the caudate-putamen. Neither hypotension nor hypoxemia were necessary for the development of morphologic injury in the brains of NPA-intoxicated rats. In fact, intoxicated rats had significantly higher systolic blood pressure and arterial blood oxygen than did controls. Arterial bicarbonate and pH were significantly lower in intoxicated rats than controls, however, suggesting that acidosis may be involved in the pathogenesis of NPA toxicity. When morphologic injury was severe, albumin extravasation was extensive occupying approximately 30%-80% of the lesion area in the caudate-putamen of NPA-intoxicated rats. When morphologic injury was mild, albumin extravasation was absent, or limited to small cuffs around individual capillaries (less than 1% of the lesion area). There was no leakage of albumin in the cerebral cortex, which was resistant to morphologic injury. It was concluded that leakage of protein-rich fluid into cerebral parenchyma from blood-brain barrier impairment is not responsible for the initiation of morphologic injury in NPA toxicity, but may contribute to the severity of injury later in the evolution of brain lesions.

Albumins↗
PubMed1995

Brain-stem auditory evoked potential monitoring. Variations of stimulus artifact in brain death.

Brain-stem auditory evoked potentials (BAEPs) were recorded in 20 subjects with brain death (mean age, 33.2 +/- 15.1 years) and 20 healthy volunteers (mean age, 29.8 +/- 6.8 years). Brain death was due to head injury (n = 14), encephalitis (n = 3), brain-stem hemorrhage (n = 1), cerebellar hemorrhage (n = 1) or cerebral infarction (n = 1). The presence, latency and amplitude of the individual BAEP components and variations of the stimulus artifact were evaluated. The mean (+/- S.D.) amplitude of the stimulus artifact was 0.26 +/- 0.12 microV in the brain-dead subjects and 0.09 +/- 0.05 microV in the control group (P < 0.001, t test). The causes of the phenomenon of increasing stimulus artifacts in the evolution of brain death remain unclear.

Acoustic Stimulation↗
PubMed2001

Monitoring of brain water by chemical shift imaging during ammonia-induced brain swelling in rats after portacaval anastomosis.

Brain edema is a leading cause of death in acute liver failure (ALF). In experimental models of ALF, an increase in the content of brain water has been inferred indirectly by measuring intracranial pressure or determined directly via analysis of brain tissue postmortem. In this study, noninvasive proton two-dimensional chemical shift imaging (2-D CSI) was used to follow the time course of the development of brain edema in a well characterized model, namely ammonium acetate infusion into rats 48 to 72 h after portacaval anastomosis (PCA). Clear differences between control and experimental rat brains were observed, with an increase of brain water signal only in the parietal cortex of the PCA + ammonia group. Selective swelling of the cerebral cortex points to a cytotoxic mechanism in the evolution of brain edema in this model. CSI signal enhancement was much greater than the gravimetrically determined water content increase. The significantly greater signal change observed with 2-D CSI may reflect enhanced proton density that results from increased water content as well as edema-related alterations in water relaxation times.

Ammonia↗
PubMedDate not supplied

[A quiet clinical course in an otogenic brain abscess].

INTRODUCTION: The occurrence of otogenic intracranial complications has been significantly diminished by introduction of antibiotic therapy, improved diagnostic methods and surgical treatment of chronic otitis. Meningitis is still the most frequent otogenic intracranial complication, otogenic brain abscesses are following, while other complications occur rarely (1,2,3). Otogenic meningitis and brain abscesses are often associated, which makes the on time diagnosis of each complication harder. Mortality from otogenic brain abscesses is still relatively high, despite diagnostic and therapeutic achievements (4.5). CASE DESCRIPTION: The aim of this study is to present a patient with brain abscess, which arose quietly, as a consequence of chronic suppurative otitis and to point at possibilities of diagnostics and treatment of this complication. The diagnosis of brain abscess by clinical methods of examination is not always reliable. It is often accompanied by most severe form of meningitis, so that neurological examination, in most cases, reveals only signs of meningitis. In our patient, the abscess has been detected by computerized tomography, in its late stage, when it already had completely formed a capsule and had shown clinically manifesting focal signs. This case is interesting because of quiet and unperceived evolution of brain abscess. In the active phase of chronic suppurative otitis, the patient was receiving antibiotic therapy, which has most likely hidden the early symptoms of evolution of intracranial infections. The appearance of signs of focal intracranial infection (photophobia) required applying computerized tomography revealing brain abscess, which was clearly bounded, with a developed capsule, pointing at its late stage (about two months). These findings lead to a conclusion that an otologist should always keep in mind and check whether there is an intracranial infection in cases of active phase chronic otitis.

Adult↗
PubMed2004

Brain lactic alkalosis in Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome is a rare progressive encephalopathy characterized by acquired microcephaly, basal ganglia calcification, and chronic CSF lymphocytosis, raised levels of interferon alpha in CSF and plasma and chill-blain type lesions. A possible mechanism of injury is cytokine related microangiopathy. We report brain imaging and proton (1H) and phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) findings during the first year after birth in two patients. In patient 1 the evolution of brain metabolite ratios and intracellular pH obtained from serial 1H (long TE) and 31P MRS studies are described; in patient 2 a single 1H (short TE) MRS study is described. Imaging findings included basal ganglia calcifications, cerebral atrophy, and leukodystrophy. The MRS results demonstrated that Aicardi-Goutières syndrome is associated with reduced NAA/Cr, reflecting decreased neuronal/axonal density or viability, increased myo-inositol/Cr, reflecting gliosis or osmotic stress and a persisting brain lactic alkalosis. A brain lactic alkalosis has also been observed in those infants surviving perinatal hypoxia-ischaemia but with a poor neurodevelopmental outcome. A possible mechanism leading to brain alkalosis is up-regulation of the Na+/H+ transporter by focal areas of ischaemia related to the microangiopathy or by pro-inflammatory cytokines. Such brain alkalosis may be detrimental to cell survival and may increase glycolytic rate in astrocytes leading to an increased production of lactate.

Alkalosis↗
PubMed1991

Neuronal interconnection as a function of brain size.

The effect of increasing brain size upon the degree of interconnection between neurons is analyzed. An explicit model suggests that as the brain is scaled up there must be a corresponding fall in percent connectedness (the fraction of cells with which any one cell communicates directly). The reason for this is that if the percent connectedness is to be maintained in the face of increased neuron number, than a large fraction of any brain size increase would be spent maintaining such interconnection while the increasing axon lengths would reduce neural computational speed. One implication is that larger brains, being necessarily limited in allowable interconnectedness, may tend to show more specialization.

Animals↗
PubMed2002

Evolution of human intelligence: the roles of brain size and mental construction.

Two competing philosophical paradigms characterize approaches to the evolution of the human mind. One postulates continuity between animal and human behavioral capacities. The other assumes that humans and animals are separated by major qualitative behavioral and mental gaps. This paper presents a continuity model that suggests that expanded human mental capacities primarily reflect the increased information processing capacities of the enlarged human brain including the enlarged neocortex, cerebellum, and basal ganglia. These increased information processing capacities enhance human abilities to combine and recombine highly differentiated actions, perceptions, and concepts in order to construct larger, more complex, and highly variable behavioral units in a variety of behavioral domains including language, social intelligence, tool-making, and motor sequences. Environmental input, including self-generated input, interacts with mental constructional capacities to assure that developing humans acquire species-typical and culturally-specific behavioral patterns. This mental constructional model is compatible with our current understanding of differences between human and non-human primate brains, of human brain plasticity, and of the minimal genetic differences between humans and chimpanzees.

Animals↗
PubMed1996

Involvement of phospholipid molecular species in controlling structural order of vertebrate brain synaptic membranes during thermal evolution.

Fluorescence anisotropy parameter of [p-(6-phenyl)-1,3,5-hexatrienyl]phenyl-propionic acid (DPH-PA) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) embedded in synaptic plasma membranes prepared from brains of cold (5 degrees C) and warm (22 degrees C) adapted fish (Cyprinus carpio L.), rat (Rattus norvegicus) and bird (Branta canadensis), was studied. Fatty acid composition of total lipids as well as molecular species composition of diacyl phosphatidylcholines and phosphatidylethanolamines was also determined. The amount of long-chain polyunsaturated fatty acids decreased with increasing body temperature. There was a near-complete compensation of membrane structural order for environmental/body temperature over the evolutionary scale as seen by DPH-PA. Using TMA-DPH, the compensation was partial with rat and bird. Since DPH-PA and TMA-DPH differ in their charges, it is proposed, that the former reported membrane regions rich in cationic or zwitterionic (neutral) phospholipids and the latter, membrane regions rich in negatively charged phospholipids in the synaptic plasma membranes. Many different molecular species (20-25) of diacyl phosphatidylcholines and diacyl phosphatidylethanolamines were identified. The level of 16:0/22:6 phosphatidylcholine decreased while disaturated phosphatidylcholines increased with increase of environmental/body temperature from the fish through the bird. Level of 1-monoenoic, 2-polyenoic phosphatidylethanolamines also decreased with an increase in environmental/body temperature. Experiments using vesicles made of mixed synthetic phosphatidylcholine vesicles (16:0/16:0, 16:0/18:1, 16:0/22:6 in various proportions) showed that increase in disaturated phosphatidylcholine species does not explain the observed complete adjustment of membrane structural order in synaptic plasma membranes. Change in level of 1-monoenoic, 2-polyenoic phosphatidylethanolamines might be one of the factors involved in controlling the biophysical properties of the membrane according to the temperature.

Animals↗
PubMed2001

Could heart rate variability predict outcome in patients with severe head injury? A pilot study.

Despite major improvements in the resuscitation of patients with head injury, the outcome of patients with head trauma often remains poor and difficult to establish. Heart rate variability (HRV) analysis is a noninvasive tool used to measure autonomic nervous system (ANS) activity. The aim of this prospective study was to investigate whether HRV analysis might be a useful adjunct for predicting outcome in patients with severe head injury. Twenty patients with severe head trauma (Glasgow Coma Scale [GCS] or= 10) to HRV in patients characterized by a worsened neurologic state (GCS < 10). Statistical analysis used the Kruskal-Wallis test, P < .05. To assess whether HRV could predict evolution to brain death, receiver operating characteristic (ROC) curves were generated the day after trauma for Total Power, natural logarithm of high-frequency component of spectral analysis (LnHF), natural logarithm of low-frequency component of spectral analysis (LnLF), and root mean square for successive interval differences (rMSSD). Seven patients died between Day 1 and Day 5 after trauma. Six of those had progressed to brain death. In these six patients, at Day 1, Global HRV and parasympathetic tone were significantly higher. Referring to the area under the rMSSD ROC curve, HRV might provide useful information in predicting early evolution of patients with severe head trauma. During the awakening period, global HRV and the parasympathetic tone were significantly lower in the worsened neurologic state group. In conclusion, HRV could be helpful as a predictor of imminent brain death and a useful adjunct for predicting the outcome of patients with severe head injury.

Accidental Falls↗